Inductive tuning system



y 1939- w J. POLYDOROFF 2,158,252

INDUCTIVE TUNING SYSTEM Filed April 22, 1933 2 sheet 1 INVENTOR. WLAD/M/E \I/DOLYDOEOFE ATTORNEY.

May 16, 1939.

w. J. POLYDOROFF 2,158,252

INDUCTIVE TUNING SYSTEM 1 Filed A ril 22, 1933 2 t -Sheet? rm 1 M. A w

Ann I i l mi E illl Patented May 16, 1939 PATENT OFFICE "2.158.252 mnoc'rrvs TUNING srs'rsm Wladimlr J. Polydoroii, Johnson Laboratories, poration of Illinois Chicago, IIL, assignor to Inc., Chicago, 111., a. cor- Application April 22, 1933, Serial N0. 667,36

15 Claims.

The invention relates to radio receiving apparatus in which compressed ferromagnetic cores are utilized as the tuning means. In such apparatus, the ferromagnetic cores are arranged to be movable with respect to the inductance coils,

and the variation of the inductance, which produces the variable tuning, is brought about by varying the effective permeability of the space surrounding the coils. This method is therelo'fore conveniently called permeability tuning to distinguish it from other methods of inductance variation, and from methods in which the capacitance is varied.

The several comminuted compressed ferromagnetic cores and inductance devices which are described in this specification are disclosed in my United States Patents No. 1,982,689, for Magnetic core material; No. 2,113,603, for High-frequency inductance device; and N 0. 2,005,203, for Variable 5 inductance device: and hence no claims covering such improvements per so are herein included.

In permeability-tuned systems containing several tuned circuits and intended to be tuned by a single control handle, there arises the problem of so designing and constructing the tuning unit that'all of the circuits will be tuned very closely to the same frequency for each setting of the single control. This is accomplished partly by designing and constructing the ferromagnetic 0 cores and the inductance coils so that they will be closely alike, partly by providing a mechanism which will insure that the cores (or the coils) will move in unison, and partly by providing adjusting means so that any unavoidable discrepancles in the cores, the coils, or the operating mechanism can be compensated for.

It is an object of this invention, therefore, not only to provide suitable gang or multiple tuning means for permeability-tuned systems, but also to provide, as a part of the complete mechanism, those essential adjustments by which the ganged units may be definitely aligned, so that they will be in substantial agreement throughout the range of adjustability.

As will be better understood from what is to follow, other and further objects of the invention include the provision of alternate driving cores (or the coils) at any adjustment of the mam control han die. Still other objects of the invention, and

advantages secured by its employment, will also appear in what follows.

As has been indicated, the first essential in a manufacture of closely alike. It is recognized, however, that even with all reasonable precautions the cells will not and that, in general, some means 10 Patent No. 1,982,689 above referred to, and additional means are disclosed in this specification.

In mechanisms for permeability tuning, the

cores move in a straight line into and out of the cores on a rigid gang-plate and by providing suitable guide means so that the only motion which the gang-plate can have is one of pure translation. There are, of course, many ways of arranging mechanically for this single translatory motion of the gang-plate and its associated cores. There are also many ways of arranging to pro- (lose this translatory motion by simple driving means.

respect to its cooperating core, in order that the effect of its core may be the coils, so that all the circuits will be tuned to the same frequency for each setting of the cores. Because of the (hillculty of establishing this 4.)

the initial conditions in the several tuned circuits, is preferably made so that its capacitance is adjustable over a limited range.

In order to establish a sufficient uniformity of performance of the cores themselves, it is desirable to arrange in the design of the core bodies an adjustment by which slight differences in the effective permeability of the core can be compensated. This adjustment is available after the cores have been completely fabricated and is pref erably carried out before they are assembled on the gang-plate. It avoids the necessity for selecting a group of cores which are suihciently alike without adjustment, and insures exact agreement of the several circuits at the low-frequency end of the tuning range.

In order to secure the full advantage of the several adjustments which have been described, and in order to secure the best possible agreement of the several circuits over the tuning range, it is preferable to carry out the adjustments in a prescribed order so that each adjustment will be made at=that portion of the tuning rangewhere it is most eifective, and so that one adjustment will not aflect another. Thus, assuming that the cores have already been adjusted to have identical effective permeability, it is preferable to adjust the capacitances in the several tuned circuits with the cores at the position of their minimum effect on the inductance of the coils. This adjustment is conveniently carried out at or near the highest frequency in the range for which the receiver is designed, and consists in tuning each of the several circuits to that frequency by the adjustment of the capacitors. This takes care of any differences which may exist in the capacitances in the wiring of the several circuits.

To the extent to which the self-inductances of the coils themselves are precisely alike, the capacitors need only to be adjusted to make the capacitance values in the several circuits also alike. However, to the extent to which the inductance values are not alike, the adjustment of the capacitors will also compensate for the inductance differences. so that at the starting point, corresponding to the minimum inductance and the highest frequency, will be in exact alignment.

The relatively movable ferromagnetic cores act only upon the inductances themselves. However, each core acts to multiply the inductance value of its associated coil by a definite factor,

no matter what the inductance value may be. i

If, therefore, the inductance value in a particular circuit is low, and if that circuit has been brought into alignment with the others by adjusting its capacitor to a slightly higher value, at an initial setting corresponding to the highest frequency, then the core will operate to tune that circuit over the same range of frequencies, and finally to the same minimum frequency, as the other circuits.

It remains only to adjust the positions of the coils with respect to their cooperating cores, so that each coil is equally affected by its core. This adjustment is preferably carried out at a frequency intermediate the two ends of the tuning range, in order to establish exact agreement of the several circuits at thisthird or intermediate point.

- To summarize, therefore, agreement at the highest frequency is secured by adjustment of the capacitors, agreement at the lowest frequency is secured by adjustment of the cores, and agreement at a frequency approximately midway bethe several circuits tween the highest and the lowest frequencies is secured by adjustment of the position of the coils. With exact agreement established at these three frequencies, substantial agreement is secured throughout the tuning range.

My present invention, therefore, contemplates that reasonable care will be taken to make the inductance coils alike, and that the cores, manufactured in accordance with the above-mentioned United States patents, will also be closely alike. I then provide, in the present invention, the independent adjustments just described, in addition to mechanism for producing the necessary motion in unisonof the several cores or coils).

The invention will be better understood if reference is made to the accompanying drawings, which are illustrative of preferred embodiments, and wherein- Figure l is a plan view of an assembly of several high-frequency devices, in one unit, parts being broken away to reveal subjacent elements;

Figure 2 is a sectional view of said unit taken on the line 2-2 of Figure 1;

Figure 3 is a view, partly in section, showing means for moving the cores of said unit;

Figure 4 is a sectional view taken on,the line 4-4 of Figure 3;

Figure 5 is a sectional view taken on the line 5-5 of Figure 1, showing an indicator and other parts in elevation;

Figures 6 and 7 are views showing core-actuating devices either of which may be substituted for the device shown in Figures 3 and 4;

Figures 8 and 9 show certain modifications of the tuning elements;

Figure 10 shows diagrammatically a receiving circuit employing one of the new high-frequency units; and

Figure 11 shows a modification of the highfrequency device.

The unit disclosed in Figures 1 and 2 has four shielded variable inductance devices arranged to operate simultaneously. This unit has a foundation platel that is provided with flanges 2 to which rectangular shields 3 are removably secured by friction or by other means, and with ribs 2a which serve as mountings for the semiadjustable capacitors 4. A perforated lug la rising from an edge of the plate I, enables the unit to be connected with a suitable support.

The foundation plate I also is provided with r hexagonal tubular thimbles 5 through each of which extends a longitudinally movable screwthreaded rod 6 which terminates outside of the foundation plate I, where it is provided with an adjusting nut 1. Fixed to the inner end of each of therods E, is a coil form 8 having a hexagonal cavity 9 into which the hexagonal thimble 5 extends, the depth of this cavity being such as to permit the coil form to move longitudinally relatively to said thimble, but without disengagement therewith, the coil form, while thus moving, being prevented from rotating by its hexagonal engagement with the thimble. A helical spring Ill is disposed between the foundation plate I and each of the coil forms 8, in order to maintain the coil forms in their adjusted positions. Each of the coil forms 8 has a flared wall If and is open at the end If, and carries an inductance coil i3. The mechanism just described constitutes means for adjusting the positions of each of the coils I3 individually with reference to the core portions 34, 39.

The foundation plate i, furthermore, is provided with tubular sockets M for guide rods I5 the mechanism for relative between the several coils and which are parts of motion in unison cores of the unit.

The flanges 2, the hexagonal tubular thimble 5, and the tubular sockets i 4 may be made integral with the plate I, as by die casting, or may be separately produced and secured to the plate in any suitable manner.

Associated with and movable toward and from the foundation plate I, is a preferably integral rectangular gang-plate ii, to which a jointed actuating rod i9 is attached. The gang-plate l8 has holes 20 in which the ends of guide tubes II are fixedly secured. The guide rods is, carried by the foundation plate I, telescope with and accurately flt these guide tubes.

As detailedin Figs. 3 and 4, mounted on the foundation plate I is a three-sided housing 23 having a flange 23a secured to the plate by screws 23b and containing the devices for reciprocating the actuating rod I 3 and the gangplate 16 to which the rod 9 is attached, these devices being a driving shaft 25 in the sides 26 01 the housing and fixedly carrying a sleeve 21 which is provided with a guide groove 28 for the actuating 29 pivoted on and extending through the slot 30 of a curved pressure-producing spring 3|, which spring is attached at one end 32 to the rear wall of the housing 23, and, at its other and free end 33, bears against the rear wall.

Carried by the gang-plate ii, are compressed ferromagnetic cores 53, preferably of the type having variable magnetic density along the magnetic path, and all closely alike. These magnetic cores cooperate with the inductance coils l3 in such a way as to vary the efiective permeability of the space surrounding the coils. Each ferromagnetic core has a cup-shaped shell 34 open at one end to receive the coil l3 and has, in its head 36, an internally threaded bushing 31 through which a screw-threaded rod 38 extends, and in which therod 38 is longitudinally adjustable.

Each core 58 also includes a plug 39 which is ening the nut 4| until it looks these parts together.

The core may thus be matched with other cores of the same unit so as to insure uniform maximum values 01' inductance in all of the variable inductance devices. This is accomplished by appropriately regulating theair gap 32 between the plug 33 and the head 38 of the shell 34, and then locking these parts together arrangement just described whereby the core portions 34, so that the cores will have by the nut 4|.

constitutes means 33 may be adjusted the same eflective permeability value.

16 is provided with outer ends of the be passed when the The rectangular gang-plate holes 42 through which the screw-threaded rods 33 may core portions 34, 38 areplaced in position, nuts 24 having bearings rod [9, and an idler 43 being screwed onto those ends to thereby firmly unite the gang-plate I3, the core portions 34, 39 and the insulating washer 43.

When cores and coils are assembled, as hereinhowever positioned, will produce substantially the same/inductance variations. These uniform results may be secured by the adjustment 0! the nuts 1 and consequent linear movement of each coil form 8 with its coil i3.

Referring to Fig. 5, the movement of the cores relatively to the coil forms 8 and the coils gang-plate i6 is provided. A scale various positions of the ly, of the gang-plate l6 and the cores other types of indicator, of course, factorily employed.

Modifications of the actuating devices shown in Figures 1, 2, 3,and 4 are revealed in Figures 6 and 7.

Figure 6 shows a rack Illa secured at one end to the gang-plate l6, and having teeth Nb which are held engaged with a pinion 21a carried by a driving shaft 24a, by a spring secured to the rear wall of said housing 23,

parts a linear movement to the rack Na, and moves the gang-plate i6 and the parts mounted thereon relatively to the other parts of the device.

Figure '7 shows a screw-threaded rotary shaft 49 extending at one end through the plate I and provided at the internally screw-threaded sleeve 5|, fixed to the gang-plate I 6. Many other forms of driving mechanism may be employed. The three forms above described are preferred for simplicity and eflectiveness.

The capacitors 4 may be of the semi-adjustable type, each having at least two plates 53 spaced by an insulator and resiliently held at any desired separation by a screw 54. The adjustable capacimeans whereby the several be tuned to'the same frequency at the high-frequency end of the tuning range.

Each of these capacitors is desirably disposed within one oi the shields 3,

shields have holes 34: justing screws 54.

In some cases it is desirable to have two values of capacitance in each circuit, as shown in Figures 8 and 9.

Figure 8 shows two capacitors 4a, lb-hav1ng diiferent capacitance values, which capacitors are of the same design as the capacitor 4, already described, and are similarly mounted on ribs 2a;

Figure 9 also reveals two capacitors 4a, 4b having either the same or diilerent capacitance values, both mounted on a common insulating base 4c. The plug of the i'erromagnetic core and the coil i3a may, as shown in Figure 8, be cylindrical, and the coil may be bank-wound, with several layers of wire.

other end with a knob 53. An

Figure 9 illustrates means which may be substituted for the devices shown in Figure 2 for preventing the coil forms I from rotating while being adjusted, the hexagonal thlmble and the hexagonal cavity I! being superseded by a bushing it fixed within the base 40 and having an internal longitudinal groove 60 with which a pin H, on the screw-threaded rod 8, engages. Any other suitable means for preventing rotation of the coilduring adjustment may be employed.

Figure 10 shows a circuit arrangement having a plurality of resonant circuits tuned by variable inductance devices such for example as those of Figs. 1 and 2, and having the three adjustments 7 above described for securing alignment between the several circuits. The cores 56 will have provision for adjustment of their eflectlve permeabilities, the capacitors 51 will have means for the adjustment of their capacitance values, and

means will be provided for the adjustment of the relative position of each core 58, with respect to its coil I3. In a preferred embodiment of the circuit of Fig. 10, these adjustments will have the ram described in can tion withFigs. I, 2 and 9. The motion of the several cores it relatively to the cells It, to tune the system over a range of frequencies, will be secured by employing the drive arrangements described in connection with Figs. 1, 2, 3, 4, 6 and 7, and an indicator will be provided as described in connection with Fig. 5. It will be understood that equivalent arrangements for the adjustments. the drive and the indicator mayebeemployed without departing from the scope of my invention.

In certain cases, as for example in superheterodyne circuits, it is necessary to have one tuned circuit cover a different range'of frequencies from the other tuned circuits, although the two ranges may overlap to some extent. In such a superheterodyne signed to cover the range from ficllto cc kilocycies. and this will require an inductance variatien of (GDP/(5509, or L45. Ifthe intermediets-frequency amplifier is designed for a frequency of 115 ltllocycles, the oscillator circuit will require to be tuned from l500+l l5 kilocycles to 550+ 2'75 kiloeycies. which requires an inductance variation of only 5-.85. To obtain this range with a variable inductance device of the same type as 'used in the preselector, an additional fixed inductance coil, not acted upon by the moving core, may be inserted in the circuit in series with the coil of the variable inductance device.

when a sufficiently high intermediate frequency is employed in superheterodyne circuits, such for example as 450 or 500 kilocycles, the inductance variation necessary in the oscillator is only of the order of 4 and may easily be accomplished by the use of the inner plug alone. In this case, similar coils may be employed for the preseleetor and for the oscillator, as shown in Figure 11, the plug It, which is used to tune the oscillator circuit, being given a suitable shape to produce the desired variations throughout the range of frequencies to be covered by the oscillator.

Having thus described my invention, claim is:

l. A plurality of resonant circuits tunablepver a range of frequencies by a tuning means which simultaneousb varies the efl'ective value of the inductance in each of said circuits, electrical means for adjusting all of said circuits to substantially the same maximum frequency, magnetic means for adjusting all of said circuits to substantially the same minimum frequency, and

what I circuit, the preselector may be demechanical means for adjusting all of said circuits to substantially the same frequency intermediate said maximum and said minimum frequencles.

2. A tuning unit for a radio receiver including a plurality of resonant circuits tunable over a. range of frequencies by tuning means which simultaneously varies the effective value of the inductance in each of said resonant circuits, said tuning meansincluding inductance coils and cooperating ferromagnetic cores and means for effectlng relative motion in unison therebetween. means for adjusting the relative position of each cooperating coil and core, means for adjusting the capacitance value in each of said resonant circuits, and means for adjusting the effective permeability of each of said cores.

3. A tuning unit for a radio receiver, including a plurality of resonant circuits tunable over a range of frequencies by tuning means which 51- multaneously varies the effective value of the inductaneeln each of said resonant circuits, said tuning means including a ferromagnetic core for each of said resonant circuits, said cores each having an adjustable air gap by which said cores may be adjusted to be effectively alike.

4. A tuning unit for a radio receiver, including a plurality of resonant circuits tunable over a range of frequencies by tuning means which simultaneously varies the effective value of the inductance in each of said resonant circuits, said tuning means including a foundation plate and aninductance cell for each of said resonant circuits, said coils each including a form, an adjusting screw and guide means, and being adjustably mountedupon said foundation plate.

5. A tuning unit for a radio receiver, including a plurality of resonant circuits tunable over a range of frequencies by tuning means which simultaneously varies the effective value of the inductance in each of said circuits, said tuning means including plural inductance coils each having a form, a winding, a guiding means, a spring member and a screw-threaded member for adjustably securing said coil, against the action of said spring member, to a foundation plate.

6. A tuning unit for a radio receiver, includinga plurality of resonant circuits tunable over a range of frequencies by tuning means which simultaneously varies the effective value of the inductance in each of said circuits, said tuning means-including a carrier, plural ferromagnetic cores-each having a screwthreaded member in two portions thereof to adjustably establish an air gap between said members and to mount said core upon said carrier, and additional screwthreaded members to lock said air gap at its adjusted dimension and to secure said core to said carrier.

1. In a plurality of resonant circuits each having a capacitor, an inductance coil and a ferromagnetic core cooperating with said cell, said cores being arranged for motion in unison relatively to said coils to tune said circuits from a minimum frequency to a maximum frequency, the method of correcting inaccuracies of alignment between said circuits which consists in adjusting the capacitance value in each of said circuits, adjusting the effective permeability of each of said cores and adjusting the relative position of each cooperating coil and core, to secure substantial alignment at said maximum frequency. at said minimum frequency and at a frequency intermediate said minimum and maximum frequencies.

5. In a plurality of resonant circuits each hav- Iii the method of correcting inaccuracies of alignment between said circuits which consists in adjusting the capacitance value in each of said circuits at said maximum frequency, adjusting the effective permeability of each of said cores at said minimum frequency and adjusting the relative position of each cooperating coil and core at a frequency intermediate said minimum and maximum frequencies.

9. A high-frequency network including plural units each having inductance and capacitance, tunable over a range of frequencies by tuning means which simultaneously varies the effective values of said inductances, electrical means for adjusting at least one of said units to have a desired maximum frequency, magnetic means for adjusting at least one of said units to have a desired minimum frequency, and mechanical means for adjusting at least one of said units to have a desired frequency at a point intermediate said maximum and minimum frequencies.

10. A high-frequency network including plural units each having capacitance and inductance, responsive to a relatively narrow band of frequencies but tunable over a quencies by simultaneous variation of the effective values of said inductances, electrical means for adjusting at least one of said units to have a desired maximum frequency, magnetic means for adjusting at least one of said units to have a desired minimum frequency, and mechanical means for adjusting at least one of said units to have a desired frequency at a point intermediate said minimum and maximum frequencies.

11. A tuning unit for a radio receiver, including a high-frequency network comprising capacitances and inductances, tunable over a range of frequencies by ferromagnetic cores which vary the effective values of said lnductances, means for adjusting the relative position of each cooperating coil and core, means for adjusting the values of the capacitances, and means for adjusting the effective permeability of each of said cores.

12. A tuning unit for a radio receiver, includ- Wide range of ire-- ing a high-frequency network comprising capacitances and inductances, responsive to a relatively narrow band of frequencies but tunable over a wide range of frequencies by ferromagnetic "cores which simultaneously vary the effective values of said inductances, means for adjusting the relative position of each cooperating coil and core, means for adjusting the values of the capacitances, and means for adjusting the effective permeability of each of said cores.

13. A tuning unit for a radio receiver, comprising a plurality of resonant circuits each including an adjustable capacitor and an inductance coil, a plate supporting said capacitors and said inductance coils, means for adjusting the position of said inductance coils relatively to said plate, inductance-varying ferromagnetic cores associated with and movable relatively to each of said inductance coils, said cores including an adjustment of their inductance-varying effect, a carrier to which said cores are secured, guides to limit the motion of said carrier to a direction parallel to the axes of said inductance coils, and means for producing said motion. I

14. A tuning unit for a radio receiver, comprising a plurality of resonant circuits each including an adjustable capacitor and an inductance coil, a plate supporting said capacitors and said inductance coils, means for adjusting the positionof at least one of said inductance coils relatively to said plate, an inductance-varying element for each of said inductance coils, at least one of said elements having an adjustment to establish its inductance-varying effect, means for moving said elements in unison relatively to said inductance coils including a carrier to which said elements are secured, and a driving member which engages a portion of said carrier.

15. A tuning unit for a radio receiver, including a plurality of resonant circuits tunable over a range of frequencies by tuning means which simultaneously varies the effective value of the inductance in each of said circuits, electrical means for adjusting said circuits to a maximum frequency, magnetic means for adjusting said circuits to a minimum frequency and mechanical means for adjusting said circuits to a frequency intermediate said maximum and minimum frequencies.

WLADIMIR J. PoLYnoRoFr'.

CERTIFICATE or CORRECTION. Patent No. 2,158,252. May 16, 19 9.

wILADmm J. rounoaorr.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, line 20, strike out the word "and"; and second column, line 51, before "means" insert mounting; page 2, second column, lineh9, strike out the after "plate 1''; page 5 first column, line-22, for rod 9" read rod 19; and'secondcolumn, line 68, after "2a" strike out the semicolon and insert instead a period; and that the said Letters Patent should be read with this correction therein that the ssme may conform to the record of the case in the Patent 'Office.

Signed and sealed this 1 th day oi July, A.D. 1959.

. v Henry Van Arsdale 1) Acting Commissioner of Patents. 

